Hydrodynamic bearing device, spindle motor, and information recording and reproducing apparatus

A hydrodynamic bearing device, comprising:

• a sleeve having a bearing hole;
• a shaft that is inserted into the bearing hole in a state of being capable of rotating relative to the sleeve;
• a thrust bearing portion having a hydrodynamic groove that generates pressure in an axial direction;
• and
• a lubricating fluid adapted to be held in a gap formed by at least the thrust bearing portion,
• the device being configured such that the value of a function F7 expressed by Formula 4 as follows is within a specific range.
• F7=F2×Ro/At (4)
• F2=S2×Pz/(C2×η×(Ro4−Ri4)) (5)
• At=π×(Ro2−Ri2) (6)
• S:
• thrust bearing face tilt amount
• S=θ×2×Ro (7)
• θ:
• thrust bearing face tilt angle
• θ(rad)=(0.0002 (mm)/thrust bearing outside diameter (mm))
• Pz:
• total thrust load (N)
• C:
• correction coefficient=0.10
• η:
• lubricating fluid viscosity (N·S/mm2)
• Ro:
• thrust hydrodynamic groove outer peripheral radius (m)
• Ri:
• thrust hydrodynamic groove inner peripheral radius (m)